Voltage regulator



Nov, 3, 1942.

w. H; SMITH VOLTAGE REGULATGR Filed April 18, 1939 3 Sheets-Sheet l I Waiter Smit/z.

BY M ATToRNEy Nov. 3, 1,942.A w. H. SMITH 2,300,471

lvENToR Walter' /z 5771272.

.ATTORNEY WITNESSES:

NGV. 3, l `W. H. SMITH I VOLTAGE REGULATOR l Filed April 18, 1939 3 Sheets-Sheet 3 I'i'i" lllllllllllllllllllllllll Arlalalflllilw wlmssis: www@ 1 Walz?? f. ST/mn?.

TTORN EY Patented Nov. 3., 1942 VOLTAGE REGULATOR Waiter H. smith, wukinsburg, ra., assignor'to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 1S, 1939, 'Serial No. 268,550

2 Claims.

This invention relates to regulating apparatus such as is adapted for regulating the output voltage of Variable speed generators. In Certain electrical generator applications, it is desirable to drive the generator at Varying speeds. For example, in generators employed on vehicles it is convenient to drive the generator at a speed that varies in accordance with the speed of the vehicle. Such generators may be employed for supplying electric energy to circuits, to which electric lamps and other electrical apparatus are connected and for supplying energy to a storage battery connected to the circuit, which battery receives energy from the generator when the generator is operating at normal voltage and speed, and supplies energy to the circuit when the vehicle and generator are not in motion or are operating at a speed below that necessary to de- Velop the Voltage required for supplying the circuit.

When a shunt-wound excited variable speed generator is used in a system of the character described, it is desirable to provide a maximum eld excitation during the starting of the generator until the voltage builds up to a normal value. It is desirable, therefore, to provide a minimum amount of regulating resistance in the generator eld circuit in order that the generator voltage may build up to normal line circuit Voltage at as low a generator speed as possible. sirable to control the generator excitation to maintain a substantially constant Voltage output therefrom at speeds above the minimum at which the desired voltage may be developed and to modify this value in accordance with the current output from the generator so as to limit, for example, the rate of charge of a battery connected to it. In regulator systems of the character indicated in which the field excitation is controlled by a variable regulating resistor in the generator field oirouit, such as a stack of carbon or graphite discs, the increasing force on the regulating resistor while the generator is below the speed necessary to develop the desired or line circuit voltage, tends to vary the resistance in the field winding circuit before the generator voltage has built up to its desired value, thus increasing the generator speed required to develop full voltage. 'In the herein described regulator, means is provided to delay the change in `field resistance value during the increase in generator voltage until that voltage has substantially reached its desired value. Means is also provided to decrease the friction of movement of the resistor discs so as to increase It is also dethe sensitivity of regulationy by permitting a 55 greater and more accurate change in resistance upon a small change in pressure on the stack. Thus, a small amount of energy and a small movement of the control element is effective to develop a large correction in field excitation.

An object of the invention is the provision of a regulator of the character indicated in which the generated voltage will build up rapidly to its desired value upon an increase in the generator speed from a low Value, and will thereafter be accurately maintained at the desired value.

A further object of the invention is the provision of a regulator of the character indicated that is effective to control the field excitation of a generator to limit both the generator voltage output and the generator current output.

A further object of the inventionis the provision of a regulator of the character indicated that is accurate in operation and sensitive to slight changes in the applied force and that requires a small amount of energy to operate.

Other objects and advantages of the invention will be apparent from the following description of preferred embodiments thereof, reference being had to the accompanying drawings, in which Figure 1 is a side elevational View of one embodiment of the invention, parts being broken away or shown in section to more clearly illustrate the structure shown.

Fig. 2 is a left elevational end view of the structure shown in Fig. 1.

Fig. 3 is a right elevational end view of the structure shown in Fig. 1.

Fig. 4 is a detail showing the means for positioning the iixed pressure plate from its supporting member.

Figs. 5 and 6 are sectional views of one embodiment of a portion of the structure that may be used in the regulator shown in Fig. 1; and,

Fig. '7 is a diagrammatic View of the circuits and apparatus employed in a regulator system governed by the regulator disclosed in Fig. 1.

Referring to the drawings and particularly to Figs. 1, 2 and 3 thereof, the regulating structure is mounted on Va panel I and consists of a carbon `or graphite stack of discs 2 which, in the ferm illustrated in Fig. 1, comprises a plurality of discs` 3 of relatively larger thickness and larger diameter than groups of discs 4 alternately positioned between the discs 3. A pressure adjusting mechanism 5 is provided at one end of the stack which includes a spring 6, one end of which engages .a bimetal temperature compensating structure 'l and the other end of which engages a yoke 8. The upper end of the yoke 8 is mounted on a pivot pin carried in a stud extending from a supporting member Iii mounted on the panel I. The lower end ol the yoke 3 connected by means of a pivot i3 to a collar i4 extending from a pressure plate i5 positioned against one end of the resistor stack and which acts against a iixed abutment or pressure plate I6 at the other end cf the stack to vary the pressure thereon.

The spring pressed yoke 8 may be moved against the bias of the spring 6 by either a voltage element |1 or a current element I6. Each of these actuating elements is provided with two coils, the voltage element I1 having a stationary coil I9 and a movable coil 20 and the current element I8 having a stationary coil 2| and a movable coil 22.

The circuits employed will be most readily understood by referring to the diagram in Fig. 7, in which the apparatus shown within the rectangle corresponds to that illustrated in Fig. 1.

In Fig. 7 a variable speed generator 23 is shown, the armature of which is driven by a shaft 24 and pulley 25, or other suitable means, from a pulley 26 on a shaft 21 that revolves in accordance with the speed of the vehicle upon which the equipment is mounted. The generator armature 23 is connected to supply energy to circuit conductors 28 and 29, one terminal of the generator being connected by conductor 3| to one terminal 32 of the current winding 2| through the opposite terminal 33 thereof to conductor 28. The three windings 22, I9 and 20 are connected in series circuit relation across the armature of the generator 23 by a circuit that extends from terminal 32 through the windings 22, I9 and 20 and by means of conductor 34, a selected portion of an adjusting resistor 35, jumper 36 between terminals 31 and 38 on the panel I and by conductor 39 to the line conductor 29. This circuit impresses a voltage on the windings 22, I9 and 20 that is a measure of the voltage of the generator 23. The excitation of the generator is controlled by a circuit extending from line conductor 29 through the generator field winding 4|, jumper 43 between terminals 44 and 45 on the panel I, conductor 46 to terminal 5| of the carbon pile stack, thence through two portions of the stack 41 and 48 that are separated by an insulating member 49 and connected in parallel between stack terminals 5| and 52, then by conductor 53, terminal 54, jumper 55, terminal 56 and conductor 51 to the line circuit conductor 28. The portion of the adjusting resistor 35 connected in series with the voltage coils 22, I9 and 20 may be varied through studs 6|, 62 and 63 provided on the panel by the use of connecting links 64 and conductors 65. The jumpers 36, 43 and 55, connecting, respectively, terminals 31 and 38, 45 and 44, and 54 and 56 are shown broken away so as to more clearly show the remaining circuits through apparatus mounted on the panel I.

Referring again to Figs. 1, 2 and 3, the voltage adjusting resistor 35 which may be of a well known cylindrical construction is carried on supports 66 and 61 that are mounted near the top of the panel I by bolts 68. The resistor discs 3 and 4 comprising the voltage regulating resistor are provided with openings 69 centrally thereof through which a metal rod 1| extends. The rod 1| is mounted on supports 12 and 13 that are attached to the panel I by any suitable means such as the screw 10. Metal sleeves and 14 are provided and attached to the metal rod 1| by any suitable means, such as pins 15 to position a tube 16 of insulating material, such as glass, which extends between the sleeves 14 through the openings 69 centrally of the discs 3 and 4, and is of lesser diameter than the diameter of the openings 69 to permit a limited movement of the discs vertically with respect to the tube 16. In order to decrease the friction that might otherwise exist between the discs 3 of resistor material and the tube 16, the several discs 3 are supported by individual cables 11, the lower ends of which are embedded in the carbon graphite discs and the upper ends of which are inserted through openings 13 in a support 19 that extends substantially parallel to the variable resistor stack and is supported from the panel I by blocks 8| that are fastened thereto by the bolts 82.

The support I2, upon which the parts of the follow-up mechanism are mounted, is attached to the supporting blocks 8| and 13, respectively. by the screws 83 and 84. The bimetal structure 'i is attached to the support I2 by bolts 85 and 08 and a spacer member 81. An opening 88 is provided in the support I2 through which the spring 6 extends, opposite ends of which press against the bimetal 1 and the movable yoke 8. The fixed abutment I6 at the right end of the resistor stack, as viewed in Fig. 1, may be rigidly supported from the block 12 by struts or bolts 89, as shown in Figs. 3 and 4.

A roller 9| is attached by the pin 92 to the lower end of the yoke 8 and is adapted to be engaged by the surface of a block 93 carried by a movable lever of the voltage element I6 comprising parallel plates 94. A contact plate 95 is also mounted on the lower end of the yoke 8 and is adapted to be engaged by the end of a rod 96, the opposite end of which is attached to a lever 91 of the current element I8.

The voltage element I1, in addition to coils I9 and 20 previously referred to, includes a magl, netic core structure having a central winding leg conductor 42, a

portion |0| which extends centrally within the coils 9 and 20, and an outer core portion |02 completing the magnetic circuit and having an annular part |03 extending about the left end of the central core portion IOI, as viewed in Fig. l, so as to completely surround the movable coil 20. The annular portion |03 of the core structure is provided with upwardly extending brackets |04 provided with a fulcrum point |05 at the point of contact between the brackets and `a square bar |06 that extends between parallel plates 94. The lower ends of the parallel members 94 are attached to opposite sides of a central sleeve |01 by rivets |08 upon which sleeve the movable coil I9 is wound. Another square bar |09 extends between the parallel members 94 above and to the left of the bar |06 as viewed in Fig. 1, one corner I|| of which provides a contact point for a hook I I2 which engages the bar |09 to actuate the lever plates 94 in a clockwise direction about the fulcrum |05 under the influence of the spring II 3 fastened between the hook member |2 and a stud II4 carried by a bimetal support II5 attached to the core structure by a screw I|6. An arm ||1 is attached to the lever 94 and is pivotally connected at its outer end by means of a pin ||8 to the cup portion ||9 of a dashpot, the inner or piston portion of which is connected by a shaft |2| to washers |22 on opposite sides of an abutment |23 carried on the panel I, between which abutment and the washers |22 centering springs |24 are provided. It will be`noted` that a line between the fulcrum point |05 of the moving arm assembly of the voltage element andthe point of contact between the hook |I2 and the moving assembly forms an acute angle with the line from contact point through the center of the spring ||3, s that, as the assembly moves in a counterclockwise direction about the pivot line |35, the lever arm through which the force of the spring II3 acts, decreases rapidly, thus compensating for any increase in spring tension occasioned byv lengthening of' the spring.

The bimetal member 1 is affected by ambient temperature to Vary the tension of the spring t so as to compensate the resistance of the resistor stack in accordance with variations in the 4ambient temperature of the air surrounding it. The bimetal structure |I5 attached to the core I|i2 of the voltage element Varies thepull on the spring ||3 in accordance with changes'in temperature of the voltage element structure so as to compensate for changes in'magnetic pull resulting from varying resistance in the w'indings I9 and 2D occasioned by changes in the temperature of the regulating element.

The current responsive element i8 is similar in general structure to that of the voltage responsive element I1 having the same core parts IDI and |02, a similar movable lever assembly mounted on brackets extending upwardly from the annular portion ID3 of the core structure, and is actuated by a similar hook II2 and spring I|3, carried by a stud I I4 mounted on a bracket extending upwardly from the core structure |02'. As best shown on the current control element I'I, each of the relay elements |1 and I8 is provided with a pin |26 extending outwardly from the lower portion of the lever for engaging the one or the other of the surfaces |21 or |28 on opposite sides of a slot in a stop member |29 for limiting the movement of the movable lever 91. The upper end of the lever 91 of the current relay element I8 is provided with an outwardly extending portion |3| to which the rod 96 is attached by any suitable means, such as a nut |32 that is screw threadedly attached to the rod 96, and a spring |33 acting between the portion |3| and nuts |34 on the outer end of the rod 96. It will be noted that the stationary winding 2| of the current relay element I8 differs from the stationary coil I9 of the voltage relay element I`| in that it consists of a few turns of the large conductor in series between the armature of the generator to the load being supplied.

Referring to Fig. '7, a battery |35 is shown connected between circuit conductors 28 and 39 and in systems of the character described automatic switching means are usually provided for disconnecting the generator from the supply circuit conductors and from the battery and other devices connected thereto when the speed of the generator is below the value necessary to develop the desired voltage of the circuit supplied therefrom. Such automatic switching means is effective to connect the generator to the supply circuit and to the battery to be charged therefrom as the generator voltage approaches the desired line circuit voltage.

It will be noted that the compression spring 6 applies maximum pressure to the variable pressure resistor when the energization of the voltage and current elements I1 and I8, respectively, are low, thus effecting maximum field and maximum generator voltage for ay given speed when the generator speed is increased from standstill to the desired value. Itv will be noted that a space exists between the roller 9| carried by the yoke 8 and the surface 93 of the block carried by the lever 94 that is actuated in a counterciockwise direction against the force of the spring ||3 upon an increase in voltage applied to the coils I9 andV 29. This space provides for an amount of movement of the lever assembly" 94 about the pivot line |05 against the bias of the spring M3 while the generator voltage is buildup from a low value to, the desired value to be maintained on the circuit, at which desired value the surface 93 engages the roller 9| to thereafter, upony further movement of the lever Se in a counterclockwise direction, move the yoke 8 and the pressure disc I5 toward the left against the bias of the spring 5 to decrease the pressure von the carbon pile stack and increase the resistance thereof, to thereby limit the generator voltage substantially to the desired value.

Upon vthe low of current from the generator 23 to the battery |35 or to other apparatus connected to the circuit conductors 23 and 29, a similar movement of the lever assembly 97 in a counterclockwise direction against the 'bias of the spring I|3 of the current relay element I8 will move the rod 96 toward the left. It will be noted that a space'is provided between the end of the rod 96 and the plate member 95 engaged thereby so as to permit a predetermined amount of movement of the rod 95 corresponding to a predetermined increase in current through the winding 2| before the current element I I3 becomes effective to move the yoke 8 toward the left about the pivot pin 9. After the current through the winding 2| has become sufficient to move the rod 96 into engagement with the contact plate 95, a further increase in current in the winding 2| causes a further movement of the rod 96 and of the yoke 8 toward the left against the compression of the spring 6, thus moving the pressure disc I5 toward the left to decrease the pressure on the carbon pile stack to correspondingly limit the current output of the generator independently of whether or not full generator voltage is maintained. It will be seen, therefore, that the regulator limits both the voltage output and the current output of the generator so as to prevent excessive voltage under all conditions and excessive current output when a low resistance load is connected to the circuit supplied by the generator.

Referring to the carbon pile stack shown in Fig. 1, the use of relatively thick and relatively large diameter discs 3 between which a plurality of thinner discs 4 of smaller outer diameter are positioned, provides a stack having desirable heat radiating characteristics in that the outer surface of the stack is increased while a relatively large number of contact surfaces are also provided.

Referring to Figs. 5 and 6, a variable resistor stack is illustrated in which discs I4| are provided that are larger in outer diameter and thicker than the groups of discs 4 and are provided with outer annular portions |42 forming cylindrical walls about the thinner discs 4. It will be noted that in Fig. 5, when the resistance of the stack is relatively high, a space |43 exists between the outer or heavier resistor elements |4I, as shown in Fig. 5, and that as the pressure on the stack is increased so as to reduce the resistance between the surfaces of the elements 4 and |4I, the outer resistor elements |4| eventually come into contact as shown at 144 in Fig. 6, thus short circuiting the discs 4 of smaller diameter and permitting a lower minimum resistor value for the stack than is obtainable with all contact surfaces in series. If desired, certain of the thinner and smaller diameter discs may be concave in form as shown at |45 to` permit a slightly greater movement of the larger resistor elements I4I than is otherwise easily obtained.

Many modifications in the circuits and apparatus disclosed within the spirit of my invention will occur to those skilled in the art and I do not Wish to be limited other than by the scope of the appended claims.

I claim as my invention:

1. In apparatus of the class described, in combination, a pressure controlled variable resistance device, biasing means for applying pressure to said resistance device and electroresponsive means for varying the pressure thereon, said variable resistance device comprising a stack 0l discs of high resistance material provided with central openings therein, an insulating member extending through said central opening to aline said discs, said stack comprising discs of relatively large diameter and thickness arranged alternately with groups of discs of relatively small diameter and thickness, and individual supporting means for suspending the discs of relatively larger diameter out of supporting engagement with the member extending centrally therethrough, said discs of larger outer diameter having annular flange portions surrounding adjacent groups of relatively thin discs and adapted upon the application of sufficient pressure to the stack to engage the next adjacent disc of like diameter.

2. In apparatus of the class described, in combination, a pressure controlled variable resistance device, biasing means for applying pressure to said resistance device and electroresponsive means for varying the pressure thereon, said variable resistance device comprising a stack of discs of high resistance material provided with central openings therein, an insulating member extending through said central opening to aline said discs, said stack comprising discs of relatively large diameter and thickness arranged alternately with groups of discs of relatively small diameter and thickness, and individual supporting means for suspending the discs of relatively larger diameter out of engagement with the member extending centrally therethrough, said discs of larger outer diameter having annular flange portions surrounding adjacent groups of relatively thin discs and adapted upon the application of sufficient pressure to the stack to engage the next adjacent disc of like diameter, certain of said thin discs being concave in shape.

WALTER H. SMITH. 

